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View Full Version : Pulled the plugs, #7 and 8 shot


ausie
06-25-2007, 07:52 AM
After my track day on Friday I did not pull as many runs as I could since the car did not seem right. Sunday morning I deceded to pull the plugs. 6 of them were in good shape and did not indicate any issues. #7 and #8 did not look so good at all, both were corroded, insulators burned above the nut and covered with a white/tan film including each spark plug bore in the head. Looked like as if water was sitting in the spark plug bores. Electrodes and ground prong were still in good shape. I sure hope I do not have a head gasket leak, oil and coolant are still clean and did not see any signs of trouble when I did an oil change two weeks ago. If the powdery substance was from water, I would suspect it was from cleaning engine bay. My thoughts on that lean towards exhaust blow-by on the plugs and probable ceramic insulator damage. Any thoughts on this would be appreciated. Thanks

Perhaps the Denso's were not up to the challenge on a stock cobra. The original factory plugs went back in since they were barely used. Car pulls amazingly better now with the different plugs.

SuperG
06-25-2007, 08:52 AM
Unfortunately, I have heard nothing but bad about Denso's (Iridium?) and I think even in 03/04's #7 and #8 are susceptible to high heat (no coolant flow). I wonder with the higher heat, that area of the gasket is prone to leakage?

InfamousSVT
06-25-2007, 03:13 PM
I recommend you go with the NGK Tr6 or an Autolite 103. They will last longer and hold up to the abuse, this is what I ran in my 04.

Also, about the #7 and #8 cylinders having water, make sure that the coil cover gasket is sealed properly when you re-install it and that no wires are keeping it from laying flat. I had that problem and the cover wasn't setted properly.

Also, do you have a head cooling mod? even flow or LCD mod?

ausie
06-26-2007, 07:20 AM
No cooling mods yet, so far do not think I have cooling issues but that will be something I do next when I get into modding the supercharger and so forth...

I have not had any issues with the car since it ran fine, just did not seem to have all the punch it did when I put the Denso's in. It has been two years since they were installed, probably my fault for not checking them periodically. I did have a the ford racing coil covers on the car for the same amount of time but removed them for cleaning and polish. It is difficult to say if the film on the plug is from water or coolant, although the top of one of the plugs close to the ceramic is rusty, the rest of the plug looks normal except for the threads which were covered with the light dusty film similar to the top of the plug. I will take pictures of the plugs when I get a chance to do so.

:D Since I still have a warranty, and if it turns out to be a head gasket leak I will get it fixed. Only mods done to the car is the cat back and aluminum expansion tank, still have the old parts if I need to put them back on I can do that.

Pro-Dyno
06-26-2007, 10:52 AM
+1 :)

I recommend you go with the NGK Tr6 or an Autolite 103. They will last longer and hold up to the abuse, this is what I ran in my 04.

Also, about the #7 and #8 cylinders having water, make sure that the coil cover gasket is sealed properly when you re-install it and that no wires are keeping it from laying flat. I had that problem and the cover wasn't setted properly.

Also, do you have a head cooling mod? even flow or LCD mod?

ausie
06-27-2007, 07:52 AM
I believe it was a seat problem of the plugs used. Tips of the plugs do not indicate any issues of abnormality. More than likely it was a bad seal. With the old factory plugs in place (were in very good condition so I reused them until I can get replacements NGK's, gap on all reused plugs was set to spec as close to 0.042 as possible). Nice response now, much higher boost level shows up on boost guage much earlier than it did. I would not doubt there was some compression loss due to the bad plugs if the deposits were from blow-by which is what it appears to look like.